import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws IOException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动");
        while (true) {
            try {
                DatagramPacket requestPacket = new DatagramPacket(new byte[1024], 1024);
                socket.receive(requestPacket);
                String request = new String(requestPacket.getData(), 0, requestPacket.getLength());
                String response = process(request);
                DatagramPacket responsePacket = new DatagramPacket(response.getBytes(), response.getBytes().length, requestPacket.getSocketAddress());
                socket.send(responsePacket);
                System.out.printf("[%s:%d]  req:%s,  resp: %s\n", requestPacket.getAddress().toString(), requestPacket.getPort(), request, response);
            } catch (IOException e) {
                System.err.println("接收数据时发生错误: " + e.getMessage());
                break;
            }
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(7788);
        server.start();
    }
}
